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Curve Tools Hand Sketching An approximation of 3D shape CAD Curves Accurate 3D shape © 2009 Autodesk 1 Why Use Curves? Curves Are Your ‘Language’ – How to Communicate Shapes to Alias The shape of the curve, combined with the ‘logic’ of the surface tool, creates a controlled shape. Mastering the creation of accurate curves will give you control of the shapes you create in 3D. © 2009 Autodesk 2 Two Types of Curves Freeform Curves Keypoint Curves Curve shape controlled by CVs © 2009 Autodesk Curve shape controlled by keypoints 3 Freeform Curves Terminology Start The first CV is displayed as The second CV is shown as Control Vertex Points used to shape the curve/surface Hull Lines connecting a row of CVs Edit Point Points showing the number of spans in a curve Span Part of a curve between two edit points Together they show the direction of the curves. Control Panel Use to change the number of spans (and therefore CVs) in a curve. At the start and end of a curve, there is a CV and an edit point. © 2009 Autodesk 4 Creating New Curves To Modify Create NURBS Curves Place 4+ CV points Pick>CV Place 2+ edit points Transform>Move Create Keypoint Curves Place 2 keypoints Keypoint Curve Toolbox >Drag Keypoints Place 3 keypoints Windows>Information> Information Window © 2009 Autodesk 5 Where to Position CVs If you want a constant, regularly changing curve shape, then the CVs should be evenly spaced, and you should have as few CVs as possible. If you need to create a strong change in the direction of a curve, you’ll need to bunch up extra CVs to control the shape. This method is okay for quick, concept modeling but not for high-quality, controllable surfaces—see the technique below. Curve 1 Curve 3 Curve 2 © 2009 Autodesk 6 One of the skills you will develop is to judge when a shape should be made out of a single curve or from separate curves joined together. Sketch Circles and Accurate Circles ‘Sketch’ Circle Not Accurate Keypoint Circle Accurate Use the ‘Sketch’ circle for circle-like shapes. Use the keypoint circle for accurate circles. Modify the keypoint circle using the keypoint tools. The keypoint circle has many spans; therefore, you typically won’t use it for sculpting. © 2009 Autodesk 7 Avoid Multi-Knots Linked Line Multi-Knot Use Separate Lines Instead © 2009 Autodesk 8 Exercises EX1-Curves.wire EX2-Curves-circles.wire EX3-Car-curves.wire EX4-Symmetrical-curves.wire EX5-Flatten-circle.wire © 2009 Autodesk 9 Curve Tools: Curve Section In this sketch, curves are drawn across each other. Even when drawing accurate curves, it is sometimes easier to draw overlapping curves and then trim them to create the final design. © 2009 Autodesk Curve Edit>Curve Section This function can be used to trim or split curves where they cross. 10 Global Curve Intersect This is a plug-in that is useful for complex layouts such as numeric keypads. Curve Techniques: Center-Line Symmetry When using the Revolve tool, having two CVs perpendicular to the rotation axis gives a smooth transition. Use snapping and mouse constraints to align the first two CVs. © 2009 Autodesk 11 Layer Symmetry If geometry is assigned to a layer, then Layer Symmetry can be used to create a mirror image. If the original geometry is modified, the mirrored geometry will update. Layers>Symmetry>Set Plane Object Edit >Align>Symmetry Plane Align To set the direction of mirroring To create a ‘tangent’ relationship between the two CVs on the center-line © 2009 Autodesk 12 Other Curve Tools Curve Edit> Add Points: Adds new CV points to the end of a curve (use with Reverse Curve) Reverse Curve: Swaps the direction of the curve Object Edit> © 2009 Autodesk Attach: Connects two curves to create a single curve (but beware, they will ‘soften’) Detach: Splits a curve into two parts Insert: Puts an extra edit point (and hence extra span and an extra CV) into a curve Extend: Lengthens or shortens a curve without changing its shape Offset: Creates a new curve, offset from the original 13 Exercises EX6-Doorknob.wire EX7-Curve-section.wire EX8-Curve-fillet.wire EX9-Offset.wire EX10-Layer-symmetry.wire © 2009 Autodesk 14 Projects P1-2D-mannequin.wire P2-Peg-and-string.wire P3-Car-badge.wire © 2009 Autodesk 15